Engine oil for LPG car

[thatfatbloke]

Someone recently advised me to check whether my LPG LS400 may need a different engine oil than the usual 5W/30 Castrol Magnatec I normally use. She's now on 157,000 miles. I personally can't see that it should ,but I thought I would check here first as I ain't no mechanic. Your thoughts please.

[Big Rat]

Hi John

LPG Converted engines run hotter and drier when in that mode, and can in some cases if the correct recommended oil is not used it can lead to valve seat recession.

Virtually all oil manufacturers have oils in their range that are suitable for example Castro GTX Modern Engine 10 W- 30.

But of course it's vital to select the one for your particular vehicle- hope this helps.

Big Rat

[sorcerer]

I've never used anything other than the oil recommended in the Owner's Manual for the car and have never had a problem with my LPG cars.

All Japanese engines can suffer from valve seat recession so if you haven't already got it, get a FlashLube kit fitted and everything will be fine.

[Haylands]

Sorry, have to disagree, LPG does run hotter than petrol, less than 10 degrees hotter, seeing as they both burn at around 1000 degrees it makes no difference at all...

The 6 cylinder 300 Lexus engine doesn't have hardened valve seats and does need a flashlube kit the 400 and 430 engine DO NOT need one, they have hardened valve seats and all you will do is coke up the engine by unnecessarily adding oil to the mix...

You do not need any special oil in an LPG vehicle, or special spark plugs either, lots of rubbish out there about it all.... just stick with standard plugs....

[Bluesman]

14 hours ago, Big Rat said:

Hi John

LPG Converted engines run hotter and drier when in that mode, and can in some cases if the correct recommended oil is not used it can lead to valve seat recession.

Virtually all oil manufacturers have oils in their range that are suitable for example Castro GTX Modern Engine 10 W- 30.

But of course it's vital to select the one for your particular vehicle- hope this helps.

Big Rat

Completely wrong. From the LPG research web site

Running Temperature of the Valve Heads and Seats

The most common misconception you'll hear about LPG is that it makes an engine run hotter than Petrol. This is no more than myth.

LPG has only 85% of the calorific value of the same amount of petrol, so it is impossible for it to create more heat. It can only make 85% as much.

 

[Bluesman]

Carry on John running the oil you have been using. I have had all my cars over the last 17 years run on LPG and have only ever used manufacturers advice as far as what engine oils to use.. Mike.

 

[Big Rat]

Always happy to bow to better knowledge, based my info on my brothers 2 X5 V8's in the states that were converted to LPG, and that was the info sheet given to him by the company that did the work, both cars subsequently suffered with valve guide problems, but that was a BMW issue which they rectified.

The incentive they had at the time was a 50 percent tax back from the government on the installation.

There we are still now that the Donald is in control over there all will be fine 😂

Big Rat

[Bluesman]

39 minutes ago, Big Rat said:

Always happy to bow to better knowledge, based my info on my brothers 2 X5 V8's in the states that were converted to LPG, and that was the info sheet given to him by the company that did the work, both cars subsequently suffered with valve guide problems, but that was a BMW issue which they rectified.

The incentive they had at the time was a 50 percent tax back from the government on the installation.

There we are still now that the Donald is in control over there all will be fine 😂

Big Rat

They obviously didn't know what they were talking about.

Valve regression is something I have never come across as the fault of running on LPG. The only cases I know of had troubles long before they were converted and the people thought that converting would solve their problems.

[Big Rat]

25 minutes ago, Bluesman said:

They obviously didn't know what they were talking about.

Valve regression is something I have never come across as the fault of running on LPG. The only cases I know of had troubles long before they were converted and the people thought that converting would solve their problems.

Certainly seems the case, doesn't it.

He my brother in California has moved the X5's on they were converted 4 years ago, has now got a pair of Toyota land Cruisers for his landscaping business, they're not converted.

At least he has now gone for Japanese reliability than the perceived German engineering, and an obvious greater ability for going off road 😏

Big Rat

[Haylands]

3 hours ago, Bluesman said:

 

LPG has only 85% of the calorific value of the same amount of petrol, so it is impossible for it to create more heat. It can only make 85% as much.

 

To be pedantic about it, yes it does have a lower calorific value which is why the old single point systems were never as powerful because you couldn't get more gas in than the throttle would allow, with a multipoint injection system the ECU uses the petrol injector times and increases them by around 20% to compensate for the lower calorific value, so theoretically it will burn hotter than petrol as the flame temp of LPG is about 10 degrees more... as I said above, pretty negligible...

Another point is that the octane rating of LPG is higher than unleaded, it's about the same as the old 5 star, on the Range Rover I have just sold I re-wrote the standard ignition map to increase the timing on acceleration and knocked nearly a second off the 0-60 time. On petrol it ran fine, as the engine (BMW M62 V8) has eight knock sensors and retarded the ignition if pre-ignition was detected.

There is an awful lot of old wives tales out there about LPG though....

[Big Rat]

2 minutes ago, Haylands said:

To be pedantic about it, yes it does have a lower calorific value which is why the old single point systems were never as powerful because you couldn't get more gas in than the throttle would allow, with a multipoint injection system the ECU uses the petrol injector times and increases them by around 20% to compensate for the lower calorific value, so theoretically it will burn hotter than petrol as the flame temp of LPG is about 10 degrees more... as I said above, pretty negligible...

Another point is that the octane rating of LPG is higher than unleaded, it's about the same as the old 5 star, on the Range Rover I have just sold I re-wrote the standard ignition map to increase the timing on acceleration and knocked nearly a second off the 0-60 time. On petrol it ran fine, as the engine (BMW M62 V8) has eight knock sensors and retarded the ignition if pre-ignition was detected.

There is an awful lot of old wives tales out there about LPG though....

This is what I like about forums that can debate without 🥊 Anyone seen some of the stuff that goes on pistonheads lately.

Nice to see all that spanner work that the 460 above is going through- great stuff.

Big Rat

 

[Bluesman]

On 25/01/2017 at 1:24 PM, Haylands said:

To be pedantic about it, yes it does have a lower calorific value which is why the old single point systems were never as powerful because you couldn't get more gas in than the throttle would allow, with a multipoint injection system the ECU uses the petrol injector times and increases them by around 20% to compensate for the lower calorific value, so theoretically it will burn hotter than petrol as the flame temp of LPG is about 10 degrees more... as I said above, pretty negligible...

Another point is that the octane rating of LPG is higher than unleaded, it's about the same as the old 5 star, on the Range Rover I have just sold I re-wrote the standard ignition map to increase the timing on acceleration and knocked nearly a second off the 0-60 time. On petrol it ran fine, as the engine (BMW M62 V8) has eight knock sensors and retarded the ignition if pre-ignition was detected.

There is an awful lot of old wives tales out there about LPG though....

Perhaps you could point me towards a web site which can back your facts up.

[Haylands]

That would involve believing things you read, it's very interesting to see all the myths repeated like chinese whispers...

What I have stated is fact and physics, I worked designing and installing LPG systems on lots of cars for years.

I don't mind if you disagree, I was just sharing my knowledge but I certainly don't want to get in an argument over something like this, you have stated your side and I have stated mine and the other members on here can make their own minds up...

[Bluesman]

1 hour ago, Haylands said:

That would involve believing things you read, it's very interesting to see all the myths repeated like chinese whispers...

What I have stated is fact and physics, I worked designing and installing LPG systems on lots of cars for years.

I don't mind if you disagree, I was just sharing my knowledge but I certainly don't want to get in an argument over something like this, you have stated your side and I have stated mine and the other members on here can make their own minds up...

Science fact states that LPG has only 85% of the calorific value of the same amount of petrol, so it is impossible for it to create more heat. It can only make 85% as much.  You cant argue against scientific fact.

[Haylands]

Like I said there are a lot of myths out there... and the calorie one is sort of misquoted... 

LPG has a specific calorific value of 46 MJ/kg

Petrol "premium" grade is 44 MJ/kg

LPG's relative density is 0.6 kg/L, Petrol is 0.7 kg/L

So, its energy density volume is lower than petrol.

Hence you have to use more, but it's specific calorific value is higher so it burns hotter...

I think that's how I remember it being explained to me, the exact values may not be spot on though...

Anyway... who cares, it's half the price of petrol and I hope they sort out a decent system for the 460 soon....

[sorcerer]

I'm not sure I agree with LPG burning just 10 degrees hotter. I've never scientifically measured it with thermometers but what I can say is that with all my petrol cars over the last 40 years I've been able to hold my hand in front of the exhaust (some old mechanics would cup their hands and bring up a handful of exhaust gases to smell). However, no way on earth can you do that with LPG as it's far too hot.

When the car goes for MOT and it's presented on gas for emissions testing, a few unsuspecting mechanics have jumped and howled when placing the probe into the exhaust pipe because they didn't expect the gases to be that hot.

[Haylands]

I would hazard a guess that it's set up lean then which will increase the EGT, can't say I ever tried a back to back but never noticed any of mine got significantly hotter..

Used to find a lot of systems set up on the lean side as it makes the cars "feel" like they are running well and helps to keep the MIL light off, which a lot of fitters are more interested in

Quick and easy to tell with a basic OBD2 reader, check the STFT, should be less than 10% but not a minus figure...

Oh and it could be more than 10 degrees, I can't remember the exact figures, my point was that at the temp they both burn at it's pretty irrelevant... 

[Bluesman]

As I have said before I will stick with a recognised body of experts Go LPG Research that LPG burning hotter than petrol is nothing more than a myth.

http://www.go-lpg.co.uk/VSR.html

 

 

 

[ambermarine]

There are conflicting opinions on this subject and I have followed with interest the views submitted by the parties concerned .My view on engine temperature, is the oil is designed for just that.

Various oils are made for different running temperatures in the engine be it diesel ,lpg, kerosene or even paraffin on the post war tractors.

The engineers who design the engines are obviously mindful of the variants on engine wear and heat is probably the biggest not so much in in the extreme but in the variance during engine warm up.

As the head is the most exposed to heat as it is where 90% of it is produced oils have to be selected for their ability to deal with the transfer of the heat from moving parts.

The expansion and contraction of those parts and over what time period is also a factor in what oil to use for example the viscosity and how that viscosity changes at different temperatures.

If Lexus have a policy not to service engines that are converted to LPG the reasons are simple,they did'nt design the engine to run on LPG so they have no expertise in what is happening to the engine during its operating cycle running on LPG.

The same can be said with regards to the oil that goes in to the engine ,so the only information on what oil to use comes from what worked historically without any manufacturers research.

Scientific data on one medium does not simply transfer to another just because it applies to the same environment.

Variances of 10% in combustion can have an effect on the oil were it matters most so I would go with the history lesson on which oil to use.

 

[dendonc]

I converted 4 years ago ( i think) i was using 5/30 then & have never changed, this is the first i have ever heard anything of the sort, i have had no probs whatsoever so i will carry on with 5/30......

[dendonc]

ambermarine

in in the extreme but in the variance during engine warm up.

Me

I always let the lpg kick in before i start driveing, which means its reached temprature..........hows that for a bit of useless info?....

[ambermarine]

Denis

Is it useless info? from a LPG user 's point of view it may be quite informative.

 

[Bluesman]

On 27/01/2017 at 9:43 AM, ambermarine said:

There are conflicting opinions on this subject and I have followed with interest the views submitted by the parties concerned .My view on engine temperature, is the oil is designed for just that.

Various oils are made for different running temperatures in the engine be it diesel ,lpg, kerosene or even paraffin on the post war tractors.

The engineers who design the engines are obviously mindful of the variants on engine wear and heat is probably the biggest not so much in in the extreme but in the variance during engine warm up.

As the head is the most exposed to heat as it is where 90% of it is produced oils have to be selected for their ability to deal with the transfer of the heat from moving parts.

The expansion and contraction of those parts and over what time period is also a factor in what oil to use for example the viscosity and how that viscosity changes at different temperatures.

If Lexus have a policy not to service engines that are converted to LPG the reasons are simple,they did'nt design the engine to run on LPG so they have no expertise in what is happening to the engine during its operating cycle running on LPG.

The same can be said with regards to the oil that goes in to the engine ,so the only information on what oil to use comes from what worked historically without any manufacturers research.

Scientific data on one medium does not simply transfer to another just because it applies to the same environment.

Variances of 10% in combustion can have an effect on the oil were it matters most so I would go with the history lesson on which oil to use.

"If Lexus have a policy not to service engines that are converted to LPG the reasons are simple,they did'nt design the engine to run on LPG so they have no expertise in what is happening to the engine during its operating cycle running on LPG"

I checked with Lexus in Reading a couple of years back and the reason they gave for this is that they are concerned that after servicing  should the car have any problems with the LPG system they would be held responsible for the problems and they just dont want that hassle.  I could quite understand their position and thought it was fair and reasonable.

 

[ambermarine]

Yes Mike

That is the dealerships polite way of telling you what Lexus say and the mantra comes from Lexus .Any company regardless as to weather its a car builder or mechanical shovel builder will not touch anything after it as been exposed to a condition it as not tested to destruction during development.

This usually refers to consumables that have not been recommended or modifications that are not type approved.

The dealership is simply making sure it does not set any precedents outside its remit,after all it is a franchise and Lexus make the rules.